Oxygen Vacancy-Induced Phase Transformations of Iron-Doped Titanium Oxide Nanostructures

Oxygen vacancies play a pivotal role in tailoring the electronic, optical, and catalytic properties of reducible metal oxides. Here, we provide a complete overview of oxygen vacancy-induced structural evolution of iron-doped titanium oxide nanomaterials with insights into their synthesis, formation, and crystallization processes. Structural analysis combining multiple techniques reveals the formation of anatase nanoparticles at low Fe loadings (i.e., ≤10 at. % Fe). At intermediate Fe concentrations (i.e., 15-20 at. % Fe), a mixture of anatase and rutile forms with the presence of extended disordered defects similar to crystallographic shear planes. These become more notable at high Fe loadings (i.e., ≥30 at. % Fe) with the complete transition to the rutile phase with a high density of defects. Moreover, we provide important information on the nucleation, growth, and crystallization processes during synthesis, emphasizing the impact of Fe atom incorporation on the TiO₂ lattice, the formation of reaction intermediates, and the structural evolution at the nano regime. The ability to control oxygen vacancies and engineer defects in Fe-doped TiO₂ allows for the optimization of charge transport, enhancing catalytic activity and tuning optical properties for applications in environmental remediation, sensing, and next-generation semiconductor technologies.